American paper towels

and R Either ethyl or methyl groups, and there are four analogues JH O All three R groups are ethyl 

JH I R and R are ethyl groups while R is a methyl group JH II R is an ethyl group, while R and R are methyl groups JH III All three are methyl groups 

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Another developmental hormone is the juvenile hormone, which predominates early in larval life later ecdysone predominates. It is a methyl ester of the epoxide of a fatty acid derivative, and there is some evidence that its structure differs in different groups of insects. By a series of coincidences, it was discovered that certain paper toweling prevented the European bug, Pyrrhocoris apterus, from developing into sexually mature adults. Instead, an extra one or two larval molts ensued, and all eventually died without being able to complete metamorphosis. The juvenility factor was traced to particular conifers used in American paper pulp, mainly Abies balsamea, Tsuga canadensis, Taxus brevifolia, and Larix laricina. The active principle was isolated and characterized. It... 

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